All this "he's going to be a stud talk", no one knows that. The same comments were said about Greg Oden and Hasheem Thabeet.
Big men generally take long to develop and whether they're kept or not, Toronto already has Ed Davis,Jonas Valancunias to add to Amir Johnson,Andrea Bargnani
and which ever FA they sign. Adding Drummond would mean you'll have to wait for him along with another rookie in Valancunias to hopefully become good core players.
Wishful thinkers hope he'll be Andrew Bynum or even Dwight Howard,but he'll likely be DeAndre Jordan.
Take Lillard,Waiters or trade down adding a starter and late teens pick,then draft Marshall or Rivers.